4-Alkyl-5,11-dihydro-6H-dipyrido[3,2-b:2',3'-e][1,4]diazepin-6-one, and their use in the treatment of HIV-1 infection are known in the prior art. These compounds are, for example, described in copending U.S. patent application Ser. No. 08/091,418 filed Jul. 13, 1993, European Patent Application No. 90 121 954.3 (publication No. 0 429 987), and by Karl D. Hargrave et al., "Novel Non-Nucleoside Inhibitors of HIV-1 Reverse Transcriptase. 1. Tricyclic Pyridobenzo- and Dipyridodiazepinones", J. Med. Chem, 34, 2231 (1991). Copending U.S. patent application Ser. No. 08/063,592, filed on May 18, 1993 describes one of several possible methods for preparing 5,11-dihydro-6H-dipyrido[3,2-b:2',3'-e][1,4]diazepines, and U.S. Pat. No. 5,200,522 describes methods for preparing 4-alkyl-3-amino-2-chloropyridines useful as intermediates in the synthesis of 5,11-dihydro-6H-dipyrido[3,2-b:2',3'-e][1,4]diazepines.